#include <bits/stdc++.h>

using namespace std;
using ll = long long;

void solve()
{
    string ss;
    cin >> ss;
    set<char> s;
    for (auto e : ss) s.insert(e);
    cout << s.size();
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
    while (t--)
    {
        solve();
    }
    return 0;
}